Diabetes mellitus is a metabolic disorder in which the ability to utilize glucose is partly or completely lost. About 5% of all people suffer from diabetes and the disorder approaches epidemic proportions.
Since the introduction of insulin in the 1920's, continuous improvements have been made in the treatment of diabetes. To help avoid high glycaemia levels, diabetic patients often practice multiple injection therapy, whereby insulin is administered with each meal. As diabetic patients have been treated with insulin for several decades, there is a major need for safe and life-quality improving insulin preparations. Among the commercially available insulin preparations, rapid-acting, intermediate-acting and prolonged-acting preparations can be mentioned.
In the treatment of diabetes mellitus, many varieties of pharmaceutical preparations of insulin have been suggested and used, such as regular insulin (such as Actrapid®), isophane insulin (designated NPH), insulin zinc suspensions (such as Semilente®, Lente®, and Ultralente®), and biphasic isophane insulin (such as NovoMix®). Human insulin analogues and derivatives have also been developed, designed for particular profiles of action, i.e. fast action or prolonged action. Some of the commercially available insulin preparations comprising such rapid acting insulin analogues include NovoRapid® (preparation of B28Asp human insulin), Humalog® (preparation of B28LysB29Pro human insulin) and Apidra® (preparation of B3LysB29Glu human insulin).
International applications WO 91/09617 and WO/9610417 (Novo Nordisk A/S) disclose insulin preparations containing nicotinamide or nicotinic acid or a salt thereof.
Most often pharmaceutical preparations of insulins are administered by subcutaneous injection. Important for the patient is the action profile of the insulin, meaning the action of insulin on glucose metabolism as a function of time from injection. In this profile, inter alia, the time of the onset, the maximum value and the total duration of action are important. In the case of bolus insulins, a variety of insulin preparations with different action profiles are desired and requested by the patients. One patient may, on the same day, use insulin preparations with very different action profiles. The action profile desired for example, depends on the time of the day and the amount and composition of the meal eaten by the patient.
Equally important for the patient is the chemical stability of the insulin preparations, for example, due to the abundant use of pen-like injection devices such as devices which contain Penfill® cartridges, in which an insulin preparation is stored until the entire cartridge is empty which may be at least 1 to 2 weeks for devices containing 1.5-3.0 ml cartridges. During storage, covalent chemical changes in the insulin structure occur. This may lead to formation of molecules which may be less active and/or potentially immunogenic such as deamidation products and higher molecular weight transformation products (dimers, polymers). Furthermore, also important is the physical stability of the insulin preparations, since long term storage may eventually lead to formation of insoluble fibrils, which are biologically inactive and potentially immunogenic.